UNISONIC TECHNOLOGIES CO., LTD MC34118 LINEAR INTEGRATED CIRCUIT VOICE SWITCHED SPEAKER-PHONE CIRCUIT DESCRIPTION DIP-28 As a voice switched speaker-phone integrated circuit, the UTC MC34118 includes the necessary amplifiers, attenuators, level detectors and control algorithm. To form the UTC MC34118’s internal circuit, there is an internal microphone amplifier with adjustable gain and mute control, internal transmit and Receive attenuators (operate in a complementary manner), level detectors at both input and output of both attenuators, and background noise monitors for both the transmit and receive channels. The dial tone can be pretended from being attenuated by the receive background noise monitor circuit by a dial tone detector. There are also two line driver amplifiers which can be used to form a hybrid network in conjunction with an external coupling transformer. A high-pass filter can be used for other filtering functions, and especially to filter out 60Hz noise in the receive channel. The UTC MC34118 which requiring typically 5mA may be operated from a power supply, or it can be powered from the telephone line. SDIP-28 SOP-28 FEATURES * Attenuator gain range: 52dB (between Transmit and Receive) * For line-powered applications : 3~6.5V low voltage operation * For improved sensitivity :4-point signal sensing * For Transmit and Receive paths: background noise monitors * External resistors set microphone amplifier gain * Mute function included * Chip disable: active or standby operation * During dial tone presence: dial tone detector to inhibit receive idle mode ORDERING INFORMATION Ordering Number Lead Free MC34118L-E28-T - Halogen Free MC34118G-D28-T MC34118G-E28-T MC34118G-S28-T MC34118G-S28-R www.unisonic.com.tw Copyright © 2014 Unisonic Technologies Co., Ltd Package Packing DIP-28 SDIP-28 SOP-28 SOP-28 Tube Tube Tube Tape Reel 1 of 15 QW-R108-007.F UNISONIC TECHNOLOGIES CO., LTD LINEAR INTEGRATED CIRCUIT MC34118 MARKING PACKAGE MARKING SOP-28 SSOP-28 DIP-28 SDIP-28 PIN CONFIGURATION FO FI CD VCC HTO+ HTOHTI TXO TXI MCO MCI MUT VLC CT 1 2 3 4 5 6 7 8 9 10 11 12 13 14 UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 28 27 26 GND 25 24 23 22 21 20 19 RLO1 18 17 16 15 CPR RLI1 TLO1 TLI1 RXO RXI RLI2 RLO2 TLO2 TL12 CPT VB 2 of 15 QW-R108-007.F UNISONIC TECHNOLOGIES CO., LTD LINEAR INTEGRATED CIRCUIT MC34118 PIN DESCRIPTION PIN NO 1 2 PIN NAME FO FI 3 CD 4 VCC 5 HTO+ 6 HTO- 7 8 HTI TXO 9 TXI 10 11 MCO MCI 12 MUT 13 VLC 14 CT 15 VB 16 17 CPT TLI2 18 TLO2 19 20 RLO2 RLI2 21 RXI 22 23 RXO TLI1 24 TLO1 25 26 27 28 RLO1 RLI1 CPR GND DESCRIPTION Output of filter. The output impedance is less than 50Ω. Input of filter. The input impedance is less than 1MΩ. Chip Disable input .A logic low (voltage lower than 0.8V) sets normal operation. A logic high (voltage higher than 2V) disable the IC. This pin’s input impedance is 90 KΩ nominally. This pin requires a supply voltage of +2.8V ~ +6.5V at 5mA. After VCC falls from 3.5V ~ 2.8V, when in the receive mode, an AGC circuit reduces the receive attenuator gain by 25dB. The output of the second hybrid amplifier. This amplifier’s gain is internally set at -1. Output of the first hybrid amplifier. This amplifier’s gain of the amplifier is set by external resistors. The first hybrid amplifier’s input and summing node. DC level is about equal to VB. The transmit attenuator’s output. DC level is about VB. The transmit attenuator’s input. It’s maximum signal level is 350 mVrms. The input impedance is 10KΩ. The microphone amplifier’s output. This amplifier’s gain is set by external resistors. The summing node of the microphone’s input. DC lever is VB. Input of mute. A logic low (voltage lower than 0.8V) sets the circuit normal operation. A logic high (voltage higher than 2V) mutes the microphone amplifier, but it doesn’t affect the rest of the circuit. The input impedance is 90 K ohms. The input of Volume control. In the receive mode, when VLC=VB, the receive attenuator is at maximum gain. The receive gain is down 35dB when VLC=0.3dB, and it does not effect the transmit modes. At this pin, to switch modes, the RC sets the response time for the circuit. In this pin, there’s an output voltage=Vcc/2 which is a system AC ground and biases the volume control. What required is a filter capacitor. The time constant for the transmit background side can be set by the RC at this pin . The input to the transmit level detector which is on the microphone/ speaker side. The output to the transmit level detector which is on the microphone/ speaker side. Also the input to the transmit background monitor. The Output of the receive level detector which is on the microphone/ speaker side The input to the receive level detector which is on the microphone/ speaker side The input to the receive attenuator and dial tone detector. In this pin, the maximum input level is 350mVrms,and the input impedance is 10KΩ. The output of the receive attenuator. This pin’s DC level is VB. The input to the transmit level detector which is on the line side. The output to the transmit level detector which is on the line side, and also the input to the transmit background monitor. The output of the receive level detector which is on the line side. The input to the receive level detector which is on the line side. The time constant for the receive background monitor can be set by the RC at this pin. Ground. UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 3 of 15 QW-R108-007.F UNISONIC TECHNOLOGIES CO., LTD LINEAR INTEGRATED CIRCUIT MC34118 BLOCK DIAGRAM MUT MCO TLI2 CT TXI TXO TLI1 HTI HTO- HTO+ 12 10 17 14 9 8 23 7 6 5 TX Attenuator MCI 11 CPT TLO2 16 Background Noise Monitor 19 CD 3 FI 2 VB Background Noise Monitor AGC 18 RLO2 VB Altenuator Conrol Level Delector 27 CPR 25 RLO1 24 TOL1 4 VCC Lever Detector RX Attenuator VB 1 20 13 22 FO RLI2 VLC RXO UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 21 26 15 RXI RLI1 VB 28 GND 4 of 15 QW-R108-007.F UNISONIC TECHNOLOGIES CO., LTD LINEAR INTEGRATED CIRCUIT MC34118 ABSOLUTE MAXIMUM RATING (TA=25°С,Voltages referred to pin 22) PARAMETER SYMBOL RATINGS UNIT Supply Voltage VCC -1~7 V Voltage at Pin 3 V3 -1~VCC+1 V Voltage at Pin 12 ( mute) V12 -1~VCC +1 V Voltage at Pin 13 ( VLC) V13 -1~VCC+0.5 V Voltage at Pin 9, Pin 21, and Pin 2 V9, 21, 2 -0.5~ VCC+0.5 V Storage Temperature TSTR -65~+150 °С Note: Absolute maximum ratings are those values beyond which the device could be permanently damaged. Absolute maximum ratings are stress ratings only and functional device operation is not implied. RECOMMENDED OPERATION CONDITIONS PARAMETER Supply Voltage Voltage at Pin 3 Voltage at Pin 12 ( MUTE) Voltage at Pin 13 ( VLC) IVB Current ( Pin 15) Attenuator Input Signal Voltage at Pin 9, Pin 21 RXO, TXO(Pin8, Pin 22) Load Current MCO(Pin 10) HTO-, HTO+(Pin 6, Pin5) Ambient Operating Temperature SYMBOL V4 V3 V12 V13 IVB V9, V21 TOPR RATINGS 3.5~6.5 0~ VCC 0~ VCC 0.3×VB~VB 500 350 0~+-2 0~+-1 0~+-0.5 -20~+60 UNIT V V V V µA mVrms mA mA mA °С ELECTRICAL CHARACTERISTICS (TA= 25°C, unless otherwise specified) PARAMETER Supply Voltages V+ Supply Current CD Input Resistance High CD Input Voltage Low VB Output Voltage SYMBOL ICC RCD VCDH VCDL VB VB Output Resistance VB Power Supply Rejection Ratio Attenuators RX Mode, RXI=150mVrms RX Mode, RXI=150mVrms Receive Attenuator Gain Change Gain AGC Gain Change (f=1kHz, VLC=VB) Idle Mode, RXI=150mVrms RX to TX Mode Range Volume Control Range RXO DC Voltage RXO DC Voltage RXO High Voltage ROVB PSRR RXO Low Voltage VRXOL RXI Input Resistance GRX GRX GRX1 GRX2 GRXI GRX3 VCR VRXO VRXO VRXOH RRXI UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw TEST CONDITIONS VCC=6.5V, CD=0.8V VCC =6.5V, CD=2V VCC =VCD=6.5V VCC =3.5V VCC =5V IVB=1mA CVB=220µF, f=1kHz VCC=5V VCC =3.5V VCC =3.5V vs. VCC =5V VCC =3.5V vs. VCC =5V MIN 50 2 1.8 4 4 -0.5 -22 49 27 RX Mode RX to TX Mode IOUT=-1mA, RXI=VB+1.5V IOUT=+1mA, RXI=VB-1V, Output Measured with Respect to VB RXI<350mVrs TYP MAX UNIT 5.5 600 90 8 800 VCC 0.8 1.3 2.1 400 54 2.4 Ω dB 6 8 6 8 0 +0.5 -25 -15 -20 -17 52 54 35 VB +-10 +-150 3.7 7 mA μA kΩ V V V dB dB dB dB dB dB dB V mV V -1.5 -1 V 10 14 kΩ 5 of 15 QW-R108-007.F UNISONIC TECHNOLOGIES CO., LTD LINEAR INTEGRATED CIRCUIT MC34118 ELECTRICAL CHARACTERISTICS(Cont.) PARAMETER Transmit Attenuator Gain (f=1kHz) TX Mode, TXI=150mVrms Idle Mode, TXI=150mVrms TX to Rx Mode Range TXO DC Voltage TXO DC Voltage TXO High Voltage TXO Low Voltage GTX GTXI GTXI VTXO VTXO VTXOH VTXOL TXI Input Resistance Gain Tracking Attenuator Control CT Voltage ( CT-VB) SYMBOL RTXI GTR RX Mode Idle Mode TX Mode TEST CONDITIONS TX TX to RX Mode IOUT=-1mA, TXI=VB+1.5V IOUT =+1mA, TXI=VB-1V, Output Measured with Respect to VB TXI<350mVrs GRX+GTX, @TX, IDIE, RX www.unisonic.com.tw TYP 4 -22 49 6 8 dB -20 -17 dB 52 54 dB VB V +-30 +-150 mV V 3.7 7 VLC=VB CT Source Current ICTR (Switching to RX Mode) CT Sink Current ICTT (Switching to TX Mode) CT Slow Idle Current ICTS CT Fast Idle Internal Resistance RFI VLC Input Current IVLC Dial Tone Detector Threshold VDT Microphone Amplifier ( VMUT< 0.8V, AVCL=31dB, unless otherwise specified) Output Offset MCOVOS VMCO-VB, RF=180 kΩ Open Loop Gain AVOLM F<100Hz Gain Bandwidth GBWM Output High Voltage VMCOH IOUT =1mA, VCC=5V Output Low Voltage VMCOL IOUT =1mA Input Bias Current IBM @MCI f=1kHz, VMUT=2V Muting(Gain) GMT 300Hz<f<10kHz MUT Input Resistance RMUT VCC=VMUT=6.5V MUT High Input Voltage VMUTH MUT Low Input Voltage VMUTL Distortion THDM 300Hz<f<10kHz HYBID AMPLIFIER HTO-Offset HVOS VHTO-~VB, RF=51kΩ HTO- to HTO+ Offset HBVOS RF =51kΩ Open Loop Gain AVOLH HTI to HTO-, F<100Hz Gain Bandwidth GBWH Closed Loop Gain AVCLH HTO- to HTO+ Input Bias Current(@HTI) IBH HTO- High Voltage VHT-H IOUT =-5mA HTO- Low Voltage VHT-L IOUT =+5mA HTO+ High Voltage VHT+H IOUT =-5mA HTO+ Low Voltage VHT+L IOUT =+5mA Distortion THDM 300Hz<f<10kHz UNISONIC TECHNOLOGIES CO., LTD MIN -85 +40 1.5 10 -50 70 MAX UNIT -1.5 -1 V 10 +-0.1 14 kΩ dB 240 0 -240 -60 +60 0 2 -60 15 0 80 1 -40 +85 3.6 20 50 3.7 200 -40 -55 50 2 0 Vcc 0.8 -0.35 0 0 80 1 0 -30 20 30 0.35 3.7 250 3.7 450 0.3 mV dB MHz V mV nA dB -68 90 0.15 -20 -30 60 mV mV mV µA µA µA kΩ nA mV kΩ V V % mV mV dB MHz dB nA V mV V mV % 6 of 15 QW-R108-007.F UNISONIC TECHNOLOGIES CO., LTD LINEAR INTEGRATED CIRCUIT MC34118 ELECTRICAL CHARACTERISTICS(Cont.) PARAMETER SYMBOL TEST CONDITIONS Level Detectors And Background Noise Monitors Transmit-Receive Switching Threshold( Ratio of Current at RLI1+RLI2 to ITH 20A at TLI1+TLI2 to Switch from Tx to Rx) Source Current at RLO1, RLO2, TLO1, TLO2 ILSO Sink Current at RLO1, RLO2, TLO1, TLO2 ILSK CPR, CPT Output Resistance RCP IOUT =1.5mA CPR, CPT Leakage Current ICPLK Filter Voltage Offset at FO FOVOS VFO-VB, 220kΩ from VB to FI FO Sink Current IFO FI Bias Current IFI SYSTEM Distortion (f=1kHz) from FI to RXO, RX Mode THDR FO connected to RXI from MCI to HTO-/HTO+, TX Mode THD includes TX attenuator MIN TYP 0.8 1 MAX UNIT 1.2 -2 4 35 -0.2 -200 150 mA µA Ω µA -90 260 -50 0 400 mV µA nA 0.5 3 % 0.8 3 % TEMPERATURE PARAMETERS PARAMETER VCC Supply Current(CD=0.8V) VCC Supply Current(CD=2V) VB Output Voltage (VCC =5V) Attenuator Gain (Max Gain) Attenuator Gain (Max Attenuation) Attenuator Input resistance Dial Tone Detector Threshold CT Source, Sink Current Microphone, Hybrid Amplifier Offset Transmit-Receive Switching Threshold Sink Current at RLO1, RLO2, TLO1, TLO2 Closed Loop Gain( HTO- to HTO+) TYP RATINGS (TA=25°С) 5mA 400µA 2.1V 6 -46dB 10kΩ 15mV ±60µA 0mV 1 4µA 0dB UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw TYP CHANGE -0.3 -0.4 +0.8 0.0008 0.004 0.6 20 -0.15 ±4 ±0.02 -10 0.001 UNIT %/°С %/°С %/°С dB/°С dB/°С %/°С µV/°С %/°С µV/°С %/°С nA/°С %/°С 7 of 15 QW-R108-007.F UNISONIC TECHNOLOGIES CO., LTD LINEAR INTEGRATED CIRCUIT MC34118 FUNCTIONAL DESCRIPTION INTRODUCTION Between operation of a speakerphone and a handset, the fundamental difference is that of half-duplex versus full-duplex. The UTC MC34118 includes the necessary level detectors, attenuators, and switching control for a properly operating speakerphone. The detection sensitivity and timing can be externally controlled. The UTC MC34118 also provides background noise monitors to make the circuit insensitive to room and line noise, hybrid amplifier to interface to Tip and Ring, the microphone amplifier, and other associated functions. ATTENUATORS The transmit and receive attenuators are complementary in function, and they are never both fully on or both fully off. For example, when one is at maximum gain: +6dB, the other is at maximum attenuation: -46dB, and vice versa. But sum of their gains remains constant at -40dB typically. To control the transmit and receive paths to provide the half-duplex operation required in speakerphone is the attenuators’ purpose. The attenuators are non-inverting, have a -3dB (from max gain) frequency of ~100kHz, their input impedance of each one is nominally 10kΩ, and to prevent distortion, their input signal should be limited to 350 mVrms(same as 990mvp-p). After the output current limit (typically 2.5mA) is reached, the output impedance is<10Ω. VB 10kΩ TXI/RXI 4.0kΩ 96KΩ To Attenuator Input These attenuators can be controlled by the Control Block’s output signal. When the CT pin which measures the signal is at +240mV with respect to VB, the circuit is in the receive mode and so receive attenuator is at +6dB. When the CT voltage is equal to VB, the circuit is in an idle mode, and it also causing the attenuators’ gains to be halfway between their fully on and fully off positions (typical -20 dB each). The most direct method to monitor the circuit’s mode is monitoring the CT voltage (with respect to VB). LEVEL DETECTORS There are two level detectors on the receive side and two level detectors on the transmit side. The terms in parentheses form one system, and the other terms form the second system. All the four level detectors are high amplifiers which have back-to-back diodes in the feedback path, and then it is resulting in non-linear gain, which permits operation over a wide dynamic range of speech levels. TLI1, TLI2, RLI1, and RLI2, the external resistor and capacitor determine the sensitivity of each level detector. Through a diode each output charges an external capacitor and limiting resistor, thus providing a DC representation of the input AC signal level. The capacitor and an internal 350Ω resistor provide the outputs’ quick rise time. And an internal current source and the capacitor set a slow decay time. On the receive side, RLI1 is at the receive input receiving the same signal as at Tip and Ring, and RLI2 is at the output of the speaker amplifier. On the transmit side, TLI2 is at the microphone amplifier, while TLI1 is at the hybrid output. UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 8 of 15 QW-R108-007.F UNISONIC TECHNOLOGIES CO., LTD LINEAR INTEGRATED CIRCUIT MC34118 FUNCTIONAL DESCRIPTION(Cont.) BACKGROUND NOISE MONITORS To distinguish speech (consists of bursts) from background noise (a relatively constant signal level) is the main purpose of the background noise monitors. There is one background noise monitor for the receive path and another one for the transmit path. The receive background noise monitor is operated on by the RLI1-RLO1 level detector, as same as the transmit background noise monitor is operated on by the TLI2-TLO2 level detector. By storing a DC voltage representative of the respective noise levels in capacitors at CPR and CPT, the background noise can be monitored. At these pins, the voltages have slow rise times which determined by the external RC, but fast decay times. The voltage at the non-inverting input of the monitor’s output comparator won’t be more positive than the voltage at CPR/CPT when the signal at RLI1/TLI2 changes slowly. But while speech is present, it will rise quicker than the voltage at the inverting input, causing its output to change. The term’s output is sensed by the attenuator Control Block. VOLUME CONTROL At VLC (pin 13) is the volume control input which is sensed as a voltage with respect to VB. Only in the receive mode the volume control affects the attenuators. In the receive mode, the receive attenuator’s gain will be +6dB, and the transmit attenuator’s gain will be -46dB when VLC is equal to VB. When VLC is reduced below VB, the receive attenuator’s gain is reduced, and the transmit attenuator’s gain is increased, but the sum of them tow remains constant. Out of the pin VLC, the bias current is typically 60nA. DIAL TONE DETECTOR This detector is a comparator with one side connected to RXI and one side input connected to VB with a 15mV offset. Under this situation: the circuit is in the receive mode, and the incoming signal is greater than 15Mv, the comparator’s output will change, disabling the receive idle mode. Then receive attenuator will be at a setting only determined by the volume control. UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 9 of 15 QW-R108-007.F UNISONIC TECHNOLOGIES CO., LTD LINEAR INTEGRATED CIRCUIT MC34118 UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 10 of 15 QW-R108-007.F UNISONIC TECHNOLOGIES CO., LTD LINEAR INTEGRATED CIRCUIT MC34118 FUNCTIONAL DESCRIPTION(Cont.) AGC The AGC circuit only affects the circuit under such situation: when the circuit is in the receive mode, and when VCC is less than 3.5v. As while as VCC falls below 3.5 volts, the transmit path attenuation changes so that the sum of the transmit and receive gains remains constant. ATTENUATOR CONTROL BLOCK This block has the seven: * C1: The output of the comparator operated by RLO2 and TLO2 (here means in microphone/ speaker side). * C2: The output of the comparator operated by RLO1 and TLO1 (here means Tip/ Ring side). * C3: The output of the transmit background noise monitor. * C4: The output of the receive background noise monitor. * Volume control * Dial tone detector * AGC circuit The C1~C4 effect is as follows: INPUTS C1 C2 C3 C4 TX TX 1 X TX RX Y Y RX TX Y Y RX RX X 1 TX TX 0 X TX RX 0 0 RX TX 0 0 RX RX X 0 Switching to the full transmit or receive from any other mode is at the fast rate (~30 ms). X :Don’t care Y :C3,C4 are not both 0 UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw OUTPUT Transmit Mode Fast Idle Mode Fast Idle Mode Receive Mode Slow Idle Mode Slow Idle Mode Slow Idle Mode Slow Idle Mode 11 of 15 QW-R108-007.F UNISONIC TECHNOLOGIES CO., LTD LINEAR INTEGRATED CIRCUIT MC34118 FUNCTIONAL DESCRIPTION(Cont.) Definition of the above is as follows: Trems Definition Transmit The transmit attenuator is fully on: +6dB. And the receive attenuator is at max. attenuation :-46dB Both attenuators are controlled by the volume control. At max. Volume the receive attenuator is fully Receive on: +6dB, and the transmit attenuator is at max.attenuation:-46dB. Both transmit and receive speech are present in approximately equal levels. Fast Idle The attenuators are quickly switched to idle until one speech level dominates the other. Speech has ceased in both transmit and receive paths. The attenuators are then slowly switched to Slow Idle the idle mode. A summary of the truth table is: 1. Under all the below situations the circuit will switch to transmit : (1) Both transmit level detectors sense signals relative to the respective receive level detectors TLI1 versus RLI1, TLI2 versus RLI2 (2) The transmit background noise monitor indicates the presence of speech. 2. Under all the below situations the circuit will switch to receive (1) Both receive level detectors sense higher signal levels relative to the respective transmit level detectors (2) The receive background noise monitor indicates the presence of speech. 3. Under all the below situations the circuit will switch to the fast Idle mode: (1) If the level detectors disagree on the relative strengths of the signal levels (2) At least one of the background noise monitor indicates speech. There are two conditions which can cause the fast idle mode to occur: (A) When both talkers are attempting to gain control of the system by talking at the same time (B) When one talker is in a very noisy environment, forcing the other to continually over-ride that noise level. In general, the fast idle mode will occur infrequently. 4. Under any of the below situations the circuit will switch to the slow idle mode (1) Both talkers are quiet( no speech present) (2) When one talker’s speech level is continuously over-ride by noise at the other speaker’s location. CT pin (pin14) determine the time required to switch the circuit between transmit, receive, fast idle, and slow idle. A schematic of the CT circuitry operates as follows: * RT =120kΩ (typ.), and CT =5µF (typ.). * Switching to the receive mode I1 is turned on; I2 is off, Charging the external capacitor to +240mV above VB An internal clamp prevents further charging of the capacitor). * Switching to the transmit mode I2 is turned on; I1 is off, Bringing down the voltage on the capacitor to -240mV with respect VB. UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 12 of 15 QW-R108-007.F UNISONIC TECHNOLOGIES CO., LTD LINEAR INTEGRATED CIRCUIT MC34118 * * FUNCTIONAL DESCRIPTION(Cont.) Switch to idle quickly, The current sources are turned off, The internal 2kΩ resistor is switched in Discharging the capacitor to VB with a time = 2kΩ x CT. Switching to idle slowly The current sources are turned off The switch at the 2kΩ resistor is open Discharging the capacitor to VB through the external resistor RT with a time=RT x CT. MICROPHONE AMPLIFIER While the inverting input and the output are pinned out, pins 10/11,the microphone amplifier, has the non-inverting input internally connected to VB. This amplifier’s open loop gain is typically 80dB when f<100Hz, and the gain bandwidth is typically 1MHz. Its maximum output swing (p-p) is typically 1 volt. MCI’s input bias current is typically 40nA out of the pin. HYBRID AMPLIFIER At HTO+, HTO-, and HTI, the two hybrid amplifiers provide the two-to-four wire converter for interfacing to the telephone line. The first amplifier’s gain is set by external resistor, and the first amplifier’s output drives the second amplifier (gain of -1). FILTER The external components determined the operation of the filter circuit. POWER SUPPLY, VB, and CHIP DISABLE For normal operation the power supply voltage is to be between 3.5v and 6.5v, but with reduced operation the VCC is possible 2.8 volts. VB’s output voltage is ~ (Vcc-0.7)/2, and also provides the AC ground. UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 13 of 15 QW-R108-007.F UNISONIC TECHNOLOGIES CO., LTD LINEAR INTEGRATED CIRCUIT MC34118 TYPICAL APPLICATION CIRCUIT UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 14 of 15 QW-R108-007.F UNISONIC TECHNOLOGIES CO., LTD LINEAR INTEGRATED CIRCUIT MC34118 UTC assumes no responsibility for equipment failures that result from using products at values that exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or other parameters) listed in products specifications of any and all UTC products described or contained herein. UTC products are not designed for use in life support appliances, devices or systems where malfunction of these products can be reasonably expected to result in personal injury. Reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. The information presented in this document does not form part of any quotation or contract, is believed to be accurate and reliable and may be changed without notice. UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 15 of 15 QW-R108-007.F